void main() {
  Map userInfo = {'age': 22, 'height': 185, 'weight': '90kg', 'username': "小帅"};

  print(userInfo);

  print(userInfo["username"]);
  userInfo['age'] = 25;
  userInfo['money'] = "15k";
  print(userInfo);

  userInfo.remove("weight");
  print(userInfo);
  
  userInfo.forEach((key,value){
    print(key);
  });

}
